A new class of acyclic (Z)-2-alkyl-1,2-diphenyl-1-(4-methanesulfonylphenyl)ethenes (7) was designed for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1 and COX-2 isozyme inhibition structure-activity studies identified (Z)-1,2-diphenyl-1-(4-methanesulfonylphenyl)oct-1-ene (7d) as a potent COX-2 inhibitor (IC(50) = 0.42 microM) with a high COX-2 selectivity index (SI > 234). In a carrageenan-induced rat paw edema assay, (Z)-7d exhibited excellent antiinflammatory activity (ID(50) = 1.1 mg/kg). The molecular modeling and structure-activity data acquired indicate that (Z)-olefins having cis C-1 4-methanesulfonylphenyl and C-2 unsubstituted phenyl (or 4-acetoxyphenyl) substituents in conjunction with a C-1 phenyl ring and a C-2 alkyl substituent of appropriate length constitute a suitable template for the design of a novel class of acyclic (Z)-2-alkyl-1,1,2-triaryleth-1-ene COX-2 inhibitors.